Add project files.

GZStudio.Core/Contracts/Services/IFileService.cs

@@ -0,0 +1,10 @@
+namespace GZStudio.Core.Contracts.Services;
+
+public interface IFileService
+{
+    T Read<T>(string folderPath, string fileName);
+
+    void Save<T>(string folderPath, string fileName, T content);
+
+    void Delete(string folderPath, string fileName);
+}